As is known, a photovoltaic apparatus comprises electric or electronic components (hereinafter in general defined as “electric loads”) which, in operation, need to be fed by an auxiliary power supply.
Typically, such an auxiliary power supply is provided by a dedicated electronic unit capable of harvesting electric power from the AC grid fed by the photovoltaic apparatus.
As is known, technical regulations require that a photovoltaic apparatus is able to operate for a relatively long period of time (ride-through time, typically equal to 1.5 s) in case of failures of the AC grid.
The provision of such a prolonged safety time interval resides in the need of allowing the photovoltaic apparatus (in particular the main power converter thereof) to implement suitable control strategies to overcome possible temporary outages of the AC grid (without interrupting its operation) or switch off in a safe manner in case of faults of the AC grid.
In order to meet these regulatory requirements, a photovoltaic apparatus might include an auxiliary power supply arrangement equipped with suitably sized energy storage means (e.g. batteries or capacitors banks) to provide the electric energy needed to operate for at least the required ride-through time.
As an alternative, a photovoltaic apparatus might include a UPS system adapted to intervene in case of failures of the AC grid.
However, as it is easy to understand, both these solutions entail remarkable disadvantages in terms of increase of the overall size and costs of the photovoltaic apparatus.
As is known, in some countries (e.g. in the USA), recent technical regulations have been introduced, which require that a photovoltaic apparatus is equipped with a protection device (e.g. a so-called RSD—Rapid Shut-down Device) capable of de-energizing the DC section (in particular the photovoltaic panels) of the photovoltaic apparatus upon a manual intervention or in case of failure of the AC grid (within a given intervention time—e.g. 10 s). Typically, these protection devices are configured as contactors configured to automatically disconnect the photovoltaic panels from the main power inverter upon a manual intervention or when an auxiliary power supply is no more present.
As it is easy to understand, in case of outages of the AC grid, also these protection devices need to be suitably fed for at least for the above mentioned ride-through time to avoid their immediate intervention and ensure a proper operation of the photovoltaic apparatus.
Of course, this fact entails an increase of the overall energy consumption of the photovoltaic apparatus during the ride-through time, which renders the above mentioned problems even more critical.
Hence, there is a need to provide a photovoltaic apparatus suitable for facing the above mentioned issues.